Irregular workpieces such as steering knuckles for automotive vehicles have been straightened at a series of stations in accordance with my prior U.S. Pat. No. 4,144,730 issued on Mar. 20, 1979. Such steering knuckles involve steel forgings having a central spindle, substantially diametrically opposed steering and caliper arms projecting radially from the spindle normal to its axis and a third support arm extending normal to the caliper and steering arms as well as the spindle. Such steering knuckles are constructed as steel forgings wherein the respective arms are subject to substantial distortions through various causes including rough handling while hot and readily deformable. The arms must be straightened before machining in order to minimize the forging stock and weight of the finished workpiece. Distortions in the steering and caliper arms may occur in either direction in each of two principal planes while the support arm normally involves distortions in either direction in a single plane. In order to achieve automatic straightening in accordance with my prior patent, a steering knuckle was transferred through a series of successive straightening stations at each of which a single arm was straightened in either direction in a single plane. For example, at a first straightening station the left hand end of a caliper arm was straightened in a vertical direction; at the next station a right hand boss of the steering arm was straightened in a vertical direction; at the next the left hand end in a horizontal direction; and finally the right hand boss in a horizontal direction. At each station the steering knuckle was rigidly clamped with the axis of the spindle primarily located in proper orientation as well as the support arm to resist torsional rotation of the workpiece about the spindle axis as a result of straightening deflection stresses in the plane of the three arms. At each station a gauge was adapted to measure the initial distortion and monitor the straightening deflection under a program adapted to employ a controlled deflection stroke providing a variable corrective deflection stroke increasing with gauged distortion determined imperically and directed toward achieving single arm single plane straightening within tolerance with a single deflection stroke. A sub-program for further corrective deflection was also provided in cases where a single deflection was not adequate.